The present invention relates to a device for measuring rotational speed and/or direction of a rolling-contact bearing.
Devices for measuring rotational speed on rolling-contact bearings are already known. Thus, a deep-groove ball bearing with an integrated sensor is shown in the FAG brochure Part No. WL 43-1206 D 97/3/97. With that sensor, it is intended to register the respective rotational speed and direction of rotation and to generate corresponding signals. In the event of failure of the sensor unit or of one of its components, the measurement is not possible or is erroneous. Thus, this apparatus cannot be used in safety-relevant applications. German Patent 195 10 717 proposes using two sensors. Here, however, these are installed in two different bearings. This is a complicated solution, as it requires two bearings. Furthermore, the design possibilities are restricted by the larger space requirement. In addition, the non-fixed connection of the two sensor bearings may cause signal differences and misinterpretations to arise.
It is an object of the present invention to provide a device without these disadvantages and, which in particular, provides an operationally reliable, compact but nonetheless simple sensor mounting.
The invention concerns a device for measuring rotation speed or rotation direction of a rolling-contact bearing which is attached to the bearing. The bearing has an inner and an outer bearing ring with a row of bearing rolling elements between them. A respective sensor unit is at each axial end of the bearing rings. Each sensor unit includes a pulse transmitter ring on one of the inner and outer bearing rings and a sensor on the other of the bearing rings. The sensor units operate independently. Each sensor unit is force-fit or positively connected to one of the bearing rings, with the pulse transmitter ring connected to one of the rings and the sensor to the other ring. Fastening two sensor units, each comprised of a pulse transmitter and a sensor, to the ends of one bearing produces a compact unit which is also cost-effective. The design freedom provided by the redundant sensor unit is considerably greater. The desired double measurement is very reliable, since signal differences and misinterpretations are forestalled by the fixed mechanical connection between the bearing and sensor parts.